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==Structure and catalytic mechanism of monodehydroascorbate reductase, MDHAR, from Oryza sativa L. japonica==
<StructureSection load='5jcm' size='340' side='right'caption='[[5jcm]], [[Resolution|resolution]] 1.90&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5jcm]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Oryza_sativa_Japonica_Group Oryza sativa Japonica Group]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5JCM OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5JCM FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.9&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=FAD:FLAVIN-ADENINE+DINUCLEOTIDE'>FAD</scene>, <scene name='pdbligand=ISD:(5R)-5-[(1R)-1,2-DIHYDROXYETHYL]-3,4-DIHYDROXYFURAN-2(5H)-ONE'>ISD</scene>, <scene name='pdbligand=NAD:NICOTINAMIDE-ADENINE-DINUCLEOTIDE'>NAD</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=5jcm FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5jcm OCA], [https://pdbe.org/5jcm PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5jcm RCSB], [https://www.ebi.ac.uk/pdbsum/5jcm PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5jcm ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/MDAR3_ORYSJ MDAR3_ORYSJ] Catalyzes the conversion of monodehydroascorbate to ascorbate, oxidizing NADH in the process. Ascorbate is a major antioxidant against reactive oxygen species (ROS) and nitric oxide (NO) (PubMed:24376554, PubMed:27652777). Can use NADPH as electron donor, but possesses lower activity compared to NADH as electron donor (PubMed:27652777).<ref>PMID:24376554</ref> <ref>PMID:27652777</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Ascorbic acid (AsA) maintains redox homeostasis by scavenging reactive oxygen species from prokaryotes to eukaryotes, especially plants. The enzyme monodehydroascorbate reductase (MDHAR) regenerates AsA by catalysing the reduction of monodehydroascorbate, using NADH or NADPH as an electron donor. The detailed recycling mechanism of MDHAR remains unclear due to lack of structural information. Here, we present the crystal structures of MDHAR in the presence of cofactors, nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+), and complexed with AsA as well as its analogue, isoascorbic acid (ISD). The overall structure of MDHAR is similar to other iron-sulphur protein reductases, except for a unique long loop of 63-80 residues, which seems to be essential in forming the active site pocket. From the structural analysis and structure-guided point mutations, we found that the Arg320 residue plays a major substrate binding role, and the Tyr349 residue mediates electron transfer from NAD(P)H to bound substrate via FAD. The enzymatic activity of MDHAR favours NADH as an electron donor over NADPH. Our results show, for the first time, structural insights into this preference. The MDHAR-ISD complex structure revealed an alternative binding conformation of ISD, compared with the MDHAR-AsA complex. This implies a broad substrate (antioxidant) specificity and resulting greater protective ability of MDHAR.

Structure and catalytic mechanism of monodehydroascorbate reductase, MDHAR, from Oryza sativa L. japonica.,Park AK, Kim IS, Do H, Jeon BW, Lee CW, Roh SJ, Shin SC, Park H, Kim YS, Kim YH, Yoon HS, Lee JH, Kim HW Sci Rep. 2016 Sep 22;6:33903. doi: 10.1038/srep33903. PMID:27652777<ref>PMID:27652777</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 5jcm" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Large Structures]]
[[Category: Oryza sativa Japonica Group]]
[[Category: Kim HW]]
[[Category: Park AK]]